Wax-oil separation



Jan- 1'3, 1953 P. $.BAcKLUND Erm.- 2,625,502

WAX-OIL SEPARATION Filed July 24, 1948 lll www

lwax cake is very voluminous and porous.

Patented Jan. 13, 1953 WAX- OIL SEPARATION Peter Stanley Backlund, LongBeach, and Vance N. Jenkins. Palos Verdes Estates, Calif., assignors toUnion Oil Company of California, Los Angeles, Calif., a corporation ofCalifornia Application July 24, 194s, serial N0.'40,475

18 Claims. 1

This invention relates to the separation of `oil and wax from wax-oilmixtures such yas waxy oils, particularly waxy distillates or waxyraflinates, or from oily waxes such as slack waxes and the like. 'Iheinvention relates particularly t0 a process for separating wax and oilfrom wax-oil mixtures to produce low pour test lubricating oils andoil-free waxes. The invention also relates -to processes for treatingwax-oil mixtures to produce high melting point waxes.

In conventional processes for separating wax from oil, the wax-oilmixture is chilled to a tem- .perature suciently low to crystallize thewax `contained in the oil. The precipitated wax is then separated fromthe oil by filtration. This lvents, however using such solvents hasnever been satisfactory because of the low Settling rates and/or longfiltering times necessary to separate wax from such solutions. Moreover,waxes separated using solvents of this type contain large proportions ofoil and are not washable on the filter.

Improved wax-oil separations are obtained by diluting the wax-oilmixtures with oxygenated or chlorinated solvents alone or together withnaphthas, benzene, toluene and the like. Thus acetone, methyl ethylketone, methyl isobutyl ketone, isopropyl alcohol, butyl alcohol,ethylene dichloride and the like solvents may be used alone or inadmixture with benzene, toluene, naphtha and the like. In practice, thesolvent is added to the wax-oil mixture and the resulting solutioncooled to cause rejection of wax, after which the separated wax isremoved by filtration. Wax precipitated from solvents consisting of orcontaining the oxygenated or chlorinated solvents is superior inltration characteristics to that separated from naphtha, benzene ortoluene but it is still in such form that on ltration the This leads torapid filtration but the cake retains a large amount of solvent anddissolved oil and it washes poorly due to the tendency of such cakes tocrack with the resultant channeling of the wash solvent. Such wax cakeshave been found .to contain 6,0% o-r more of oil. vThe Weight of zli)2,229,658 to Jenkins.

solvent present in the so-called dry cake is usually two to four timesthat of the wax present.

A modification of the process involving dewaxing with solvents isdescribed in U. S. Patent No.

This patent discloses cooling the wax-oil mixture in the substantialabsence of solvent and then adding the required amount of solvent ordiluent immediately before filtering, or cooling the wax-oil mixture andadding solvent in increments during the cooling process.

It is generally considered that Wax separates from oil, i. e. fromoilwith which it is normally associated, in a substantially oil-freecrystalline form which would be readily filterable if the oil wassufficiently non-viscous at the filtering temperature to permitltration. The object of using solvents has been to dilute the oil fromwhich the w-ax separates or has separated in order to reduce itsviscosity suiciently to permit ltration. Although, as mentioned above,naphthas, benzene and toluene have been employed as solvents it isgenerally conceded that waxes do separate from oil-wax mixtures dilutedwith these solvents, particularly the aromatic solvents, in a modiedform which is not readily lter-able. In fact, such solvents employedalone have not .found commercial utilization. In selecting solvents itis desirable that single solvents, or mixture of solvents, be employedwhich do not materially change the type of structure of the wax as itseparates from the oil or oil-wax mixture, or at least do not modify thestructure in such a way or to such .an extent as to prevent easyltration.

The oxygenated or chlorinated solvents mentioned above meet theserequirements at least to a certain degree. However, in certainoperations, particularly where low dewaxing or deoiling temperatures areemployed, the oxygenated or chlorinated solvents do not have suicientsolvency for the oil present to prevent phase separation at theextremely low temperatures. In such cases suicient good oil solvent suchas naphtha, benzene or the like is added to the oxygenated orchlorinated solvent to prevent such phase separation. In general,commercial dewaxing and deoiling processes are based on the use of mixedsolvents such as mixtures of benzene and methyl ethyl ketone. In suchcases the methyl ethyl ketone is considered the wax anti-solvent and theamount of benzene employed is insuicient to seriously alter the Waxanti-solvent properties of this ketone.

In all of the above processes it is essential `that chilling rates beclosely controlled. Too rapid chilling rates result in poorlycrystallized waxes and bulky wax cakes which crack badly and washunevenly.

It has now been discovered that improved waxoil separations can beeiiected by chilling wax-oil mixtures in the presence of an aromaticsolvent which modies the type of structure of Wax normally separatingfrom such Wax-oil mixtures, pro-v ducing a gelatinous mixture of oil,solvent and wax, which gelatinous mixture is relatively stable andsubstantially uniilterable in that extremely long ltration times arerequired and the wax cake which is formed contains extremely highproportions of oil and solvent, rendering the filter cakes unwashablewith any degree of speed or completeness, and when the proposed dewaxingor deoiling temperature has been reached adding to the chilledgelatinous mass a good wax antisolvent in an amount by volume equivalentto or greater than 1 part of anti-solvent per 1.5 parts of solvent. Uponadding these amounts of wax anti-solvent, which is precooled to aboutthe nltering temperature, the gelatinous mass is apparently convertedinto a slurry consisting of welldeiined wax crystals in a solution ofoil in the mixture vor solvents. This wax slurry is readily ulterable,having a particularly high filtration rate and forming wax cakes on theiilter which are relatively dense, non-porous and which do not crack sothat the cakes are readily washed with solvent The washed wax cakesretain extremely low proportions of oil and solvent and, afterelimination of solvent by evaporation, are found to consist ofsubstantially pure wax free from solvent and containing extremely lowproportions of oil, such as below 0.5 to 1% of oil. Apparently the Waxseparated in this manner does not retain or absorb appreciable amountsof solvent.

Furthermore, it has been discovered that when chilling a wax-oil mixturein the presence of an aromatic solvent which produces the gelatinousunlterable wax the rate of chilling may be varied over Wide limitswithout affecting the filter rate of the wax slurry produced aftermixing with wax anti-solvent and without directing the washing of thewax cake on the lter. Thus, although in conventional processes chillingrates of 1 F. to 3 F. per minute must be closely adhered to in order toproduce a iilterable wax, in the present process chilling rates as highas l F. to 15 F. per minute have been employed without deleteriouslyaffecting the filtration characteristics of the resultantwax-oil-so'lventJ mixture after mixing with a wax anti-solvent. In fact,rapid chilling appears to improve ltration characteristics in mostcases.

A fundamental discovery is, therefore, that gelatinous uniilterable orpoorly iilterable Wax may be converted into a crystalline, readilylilterable form, without altering the temperature, i

by adding to the gelatinous wax one of the wax anti-solvents describedherein. The gelatinous wax may contain, or be associated with, a lowboiling solvent and/or mineral oil. The structure of the wax whichseparates on chilling a mixture of oil, wax and a solvent such asbenzene, toluene and the like 'has been described as gelatinous.Although the exact physical form of the Wax is not known, it is observedthat when such a mixture is chilled, with or without agitation, the

Whole mass assumes a gelatinous form as a temperature is reached wherewax becomes insoluble in the mixture of solvent and oil with which itwas originally associated. Microscopic examination of chilled mixturesof Wax, oil and toluene as Well as microscopic examination while suchmixtures are being chilled, using a magnification of diameters and usingpolarized light in yorder to show more distinctly the separation of waxymasses, has failed to indicate the presence of wax crystals even attemperatures as low as 0 F. It is assumed from this and from thedescription above given, that on cooling such mixtures a gelatinousproduct is formed and it is believed that this is a reasonableinterpretation of the phenomenon which occurs.

On adding a Wax anti-solvent such as methyl ethyl ketone, in amountsgreater than about 1 part of anti-solvent to 1.5 parts of solvent byvolurne, to a gelatinous mass obtained by chilling, a mixture of wax,oil and solvent (toluene for example) there is produced a slurry whichis readily luid and apparently consists of crystalline wax suspended inthe solvent solution of oil. This again has been veriiied by microscopicexaminatio'n under the same magnification referred to above usingpolarized light for illumination of the specimens under examination.This slurry appears to contain crystalline wax masses, which masses areof uniform size and apparently not interlaced and are thus free to movein the liquid phase. Additionally, microscopic examination has been madeof the crystal formation and growth on adding a wax anti-solvent to agelatinous mass produced by chilling a mixture of wax,

voil and solvent such as toluene. In this case, al-

though no crystals are observable in the original chilled mixture at 0F., on adding wax antisolvent, precooled to the same temperature, it isobserved that crystal formation and growth is uniform and extremelyrapid.

For comparison, microscopic examination of a chilled wax slurry preparedby chilling a wax-oil mixture in the presence of toluene and methylethyl ketone showed the presence of crystalline wax masses whichappeared to be interlaced with other wax masses in such a manner thatthere appeared to be no regularity or uniformity in the Vsize of the waxmasses.

Thus, it is an object of the invention to separate wax-oil mixtures intotheir constituent components in a simpley eiiicient and economicalmanner.

It is a further object of the invention to separate wax-oil mixturesinto substantially oil-free wax and oil of low pour test.

Another object of the invention resides in dewaxing or deoiling wax-oilmixtures in the presence `of solvents of the non-viscous type andseparating wax from a solvent mixture in isuch a manner that lthe wax isin a readily lilterable, readily washable and substantially oil-freecondition.

Another object `of the invention is to convert gelatinous, unlterable orpoorly iilfterable wax into a non-gelatinous readily lterable form atsubstantially the same temperature by contacting or Ifadmixing thegelatinous Wax with a wax antisolvent.

Another object of the invention is to provide a method of wax-oilseparation involving chilling -of the wax-oil mixtures followed byltration which permits rthe use of rapid chilling rates,

Still another object of the invention is to provide a method of deoilingwaxes land ldewaxing oils which involves chilling wax-oil mixtures inthe presence of a diluent but which permits exceptionally rapid ltrationand washing rates, thus permitting a lsubstantial reduction in theltration cycle time in commercial operations, the

method comprising chilling the wax-oil mixture in the presence of anaromatic hydrocarbon solvent to lproduce a gelatinous mass and adding tothe chilled mass an amount by volume of a wax anti-solvent equal to atleast 1 part per 1.5 parts -of aromatic hydrocarbon solvent to preparethe chilled mass for filtration.

Other object-s and features of the invention will be apparent from thefollowing ldescription of the invention.

In the following description of the invention the term solvent A will beemployed to designate the aromatic hydrocarbon solvent which is added tothe wax-oil mixture before chilling and solvent B will be employed todesignate the wax anti-solvent which is added to the chilled wax-oilsolvent A mixture -to convert the gelaltinous wax precipitate in areadily ilterable crystalline form.

4Solvents which may be employed as solvent A and used during thechillin-g of the wax-oil 'solvent mixture according to this inventionar-e those which will cause the separation of the described gelatinouswax. These include the aromatic hydrocarbons benzene, toluene, mixturesof benz-ene and toluene, xylene, and even somewhat higher molecularyweight benzene homologs such as cumene. Also mixtures of low molecularweight aromatic compounds or hydrocarbon fractions containingappreciable proportions of aromatic hydrocarbons may be employed. Ofthese solvents benzene, benzene containing sufficient toluene to preventsolidiiication Iat the lower dewaxing temperatures, and toluene are thepreferred solvents. Benzene cannot be efficiently used by itself fordewaxing where the dewaxing temperature is in the range of 0 to -25 F.because of its relatively high solidication point. However, a mixturelof 90% benzene and 10% toluene may be employed for such low temperaturedewaxing operations.

Solvents which may be employed as solvent B, and are 'added to thechilled mixture of wax, oil and solvent A to convert Ithe separatedunfilterable or poorly iilterable wax into the ydesired easilyiilterable form include the wax anti-solvents, or poor wax solvents,acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methylisopropyl ketone, methyl normal butyl ketone, methyl isobutyl ketone aswell as higher ketones containing up to about 8 carbon atoms andmixtures of such ketones; propyl alcohol, butyl alcohol, amyl alcoholand mixtures of such alcohols; ethylene dichloride, trichlorethylene;various ethers such as diethyl ether, ethyl isopropyl ether and thelike. Of these solvents, the ketones are preferred an-d MEK is thelparticularly preferred solvent B.

According to the invention, separation of wax from wax-oil mixtures iseffected by chilling the wax-oil mixture to the 'desired dewaxing ordeoiling temperature in the presence of solvent A which causes theseparation of wax from oil in a gelatinous condi-tion, which wax cannotbe separated successfully from oil by filtration, and subsequentlyadding to the chilled mixture a precooled wax -antisolvent (solvent B)which has the effect Iof converting the gelatinous wax into Ia physicalfo-rm ywhich is readily filterable. The amount by volume of solvent Blapparently must be at least about 1 part per 1.5 parts of solvent A. Inother words the ratio of solvent B to solvent A in the iinal mixture tobe filtered must be at least about 0.67 to 1. Lower ratios :areapparently unsatisfactory in that they do not improve filtration rate,in fact it has been observed that using ratios of solvent B to solvent Ain the range between 0.1 to 1 and 0.5 or 0.6 to 1 filtration rates arelower than those obtained in Iconventional ydewaxing opera-tions wherethe wax-oil mixtures are chilled in the presence of wax Ianti-solvents.Apparently using the smaller ratios of solvent B the conversion of thegelatinous `wax into a readily lterable form d-oes not occur.

The temperature to which the wax-oil-solvent A mixture is cooled willdepend upon the grade of wax which it is desired to separate, and uponwhether or not a low pour point oil is to be produced. Thus, if it isdesired to separate a high melting wax from a wax-oil mixture thismixture will be cooled in the presence of solvent A to a temperaturebetween about F. and 25 F., and the required quantity of solvent B,precooled to about the same temperature, will be ladded and mixed withthe chilled `mixture in order to effect the desired change in thestructure of the separated wax. The resulting mixture will then befiltered to separate the -oil-free wax from the resulting mixture ofsolvent A, solvent B and oil still containing low melting point wax. Thewax cake is preferably washed on the filter at about the sametemperature with a small amount of solvent which is preferably a mixtureof solvent A and B, of the same composition as is present in thefiltrate. High melting point waxes separated in this m-anner have beenfound to contain less than 0.5-1.0% of oil and are light in color.Water-white marketable products may be obtained by simple treatment withfilter clay at 250 F.350 F. Such waxes have melting points in the rangeof 130 F. to 200 F. depending upon the particular wax-oil mixture beingtreated fand upon the dewaxing temperature employed.

If it is desired to recover the low melting point wax from the filtrateobtained in the-above operation, and to produce a low pour test oil, theltrate consisting of solvent A, solvent B, low melting point wax and oilis further chilled to a temperature in the range of 10 F. to 25 F. andthe chilled mixture is found to be readily iilterable, producing a waxcake of low melting point wax, i. e. melting within the range of F. toF., or possibly 130 F., which is readily washed on the iilter and isobtained substantially oil-free. Thus, after separating the high meltingpoint wax in the manner described the low melting point Wax may beseparated successfully by conventional methods. i. e., cooling in thepresence of a solvent having wax anti-solvent characteristics, toproduce a readily iilterable wax reject.

If it is desired to separate substantially all of the wax from a wax-oilmixture in one step this can be done by cooling the mixture of wax, oiland solvent A to a temperature of 10 F. to 25 F. and adding precooledsolvent B at about the same temperature as the chilled mixture, mixingto effect the conversion of separated wax into the readily lterable formand filtering. In such cases it is found that the wax, after washing andevaporating to remove solvent, is substantially oil-free. Moreover, thefiltrate consisting of oil and mixed solvent, after evaporating toremove the solvent, is low pour point, substantially completely dewaxedoil.

In its broadest aspects, the invention comprises converting gelatinous,uniilterable or poorly llterable wax into a readily iilterable, physicalform without materially changing the temperature of the system by.adding to the .gelatinous wax, or contacting the gelatinous wax with-asuicient quantity of solvent B. as for example methyl ethyl ketone,which has the .effect of converting the unflterable wax into a physicalform which permits easy removal of the Wax from any liquid phase presentby simple ltration.

The method of separation of wax-oil mixtures according to the inventionmay better be understood by reference to the drawing, which is adiagrammatic view of a system suitable for carrying out the process.Referring to the drawing, a waxy stock, for example a rafnate derived byselective Solvent extraction of an S. A. E. 50 waxy distillate producedby the vacuum distillation of a Santa Fe Springs crude oil or the rawdistillate itself, or other raw distillates or rafnates obtained fromwaxy crude oils, or the crude waxes or slack waxes obtained from suchoil, or even a crude oil residue containing wax, is maintained in tank lat a temperature suiciently high to maintain the wax in solution in theoil. The solution of wax in oil is withdrawn from its storage tankthrough line II controlled by valve I2 and is pumped by means of pump I3into chilling and mixing column I4. Column I4 is provided with a jacketI5 into which a cooling liquid may be introduced by means of line I6 andwithdrawn through line l1. Column I4 is also provided with agitating orstirring paddles and scrapers I8 on shaft I9 which is rotated by pulley28 connected to a suitable source of power not shown. Solvent A, forexample toluene, xylene, or a mixture of benzene and toluene, maintainedin tank 2| is withdrawn from tank 2l through line 22 controlled by valve23 and pumped by 4means of pump 24 into chilling and mixing column I4.The mixture of wax, oil and solvent A is chilled, with sufcientagitation to prevent the mixture setting up into a solid or non-fluidmass, to the desired dewaxing temperature.

When the desired temperature for dewaxing has been reached the chilledmixture is withdrawn from column I4 through line 25 controlled by valve26 and pumped by means of pump 21 through line 28. At the same timesolvent B, which is a wax anti-solvent, as for example methyl ethylketone, a mixture of methyl ethyl ketone and acetone, methyl propylketone, methyl isopropyl ketone or methyl isobutyl ketone is withdrawnfrom tank 29 through line 38 controlled by valve 3I and pumped by meansof pump 32 through cooler 33 where it is cooled to about the temperatureof the chilled wax-oil-solvent A mixture and passed by means of line 34into line 28 in contact with the cooled wax-oil mixture from column I4.The combined stream is passed through mixer 35 and line 35a into filter36 where the wax suspended in the mixture is separated from oil andmixed solvent. Mixer 35 may be a bafiied pipe or even a short length ofordinary piping may suce as a mixing means. The wax separated in filter36 is withdrawn via line 31, controlled by valve 38, and pumped by meansof pump 39 through heat exchanger 40 where it is heated suiiciently toeiect vaporization of any solvent remaining in the wax. The heated waxis then passed via line 4I into evaporater 42 which is provided withclosed heating coil 43 and mist extractor' 44. The solvent vapors arerecovered from the evaporator via line 45 controlled by valve 46 throughline 41, condenser 48, line 49 controlled by valve 50 and pumped throughline 5l by means of pump 52 into mixed solvent storage tank 53. Thesolvent-free wax is withdrawn from evaporator 42 through line 54,controlled by valve 55, and pumped by means of pump 56 into storage tank51.

Prior to the removal of the wax cake deposited on the filtering elementof lter 36 it is Ipreferable to wash the wax cake with a small amount ofmixed solvent which may be withdrawn from storage tank 53 through line58 contr-olled by valve 59 and forced by pump 68 through line 6Icontrolled by valve 62 through cooler 63 where the mixed solvent iscooled to the dewaxing temperature. The cooled solvent leaving cooler 63passes through line 64 controlled by valve 65 and line 35a to filter 36.The solvent containing the washed constituents of the filter cake ispassed from lter 36 into line 66 and is further handled in the mannerdescribed for the ltrate consisting of dewaxed oil and mixed solvent inthe following paragraph.

The ltrate is passed from lter 36 through line 66, controlled by valve61 into heat exchanger 68 where it is heated suciently to effectvaporization of the solvent. The heated ltrate is then passed via line69 into evaporator 'I8 which is provided with closed heating coils 1Iand mist extractor 12 in which the solvent is vaporized from the oil.The solvent-free dewaxed oil is removed from the -bottom of theevaporator through line 12 controlled by valve 13 and pumped by pump 14to dewaxed oil storage tank 15. The vaporized solvent is removed fromevaporator 18 through line 16 controlled by valve '11 and passed vialine 41 to condenser 4B and thence to mixed solvent storage tank 53 inthe manner described for the solvent vaporized from evaporator 42.

The mixed solvent, consisting of a mixture of solvent A and solvent B instorage tank 53, is separated into its components for further use in thewax-oil separati-on process by pumping the mixed solvent from tank 53 bymeans of pump 68 through line 58 controlled 'by valves 59 and 18 intodistillation column 19. This distillation column may be a plate typecolumn or a packed column such as is indicated in the drawing. Thepacking shown as 88 may be any conventional type of packing such asceramic rings, saddles, or broken ceramic fragments or the like. In thedistillation column, solvent B, as for example methyl ethyl ketone, isvaporized and passed through line 3| controlled by valve 82 throughcondenser 83 and `pumped by means of pump 84 through line 85 controlledby valve 86 into line 81 controlled by valve 88 into solvent B storagetank 29. The solvent A, as for example toluene, which is obtained as abottoms fraction in distillation column 19 is passed through line 89controlled by valve 98 through cooler 9i and pumped by means of pump 92through line 83 controlled by valve 94 and thence through line 95 intosolvent A storage tank 2 I.

The above description of the invention is conned to a case in which asingle wax fraction is desired, the single wax fraction constitutingeither substantially all of the wax present in the wax-oil mixture ormerely the high melting point wax present in the mixture. However, theprocess of this invention is applicable to the removal of two separatewax fraction-s, one consisting primarily of the high melting point waxoriginally present in the mixture and the second consisting of the lowmelting point wax present in the mixture. When such a separation isdesired complete dewaxing is not effected in the rst stage, i. e., vthestage described above, but rather in this 9.. stage the wax-oil-solventA mixture is chilledV to a temperature sufficient to reject fromsolution only the high melting point wax and the low melting point waxis removed in a second stage. In this method of operation the mixture ofoily Wax and solvent A is chilled to a temperature between 75 F. and 25F. Solvent B is added and mixed in the manner previously described toconvert the separated wax into readily lterable form and the mixture isltered to separate the high melting point wax from the mixture of oil,low melting point Wax and solvents. After Washing, the high meltingpoint Wax is removed from the lter 36 and passed through a solventrecovery stage as indicated. The iiltrate from filter 36, consisting ofoil and low melting point wax in solution in a mixture of solvent A andsolvent B is passed through line 66 and removed from this line throughline 96 controlled by valve 91 and passed into chilling and mixingcolumn 98. This column may be similar to column 4 used in the rstdewaxing stage. In column 98 the oil-wax-solvent mixture is cooled tothe desired dewaxing temperature which may be as low as 10 F. to 25 F.or 30 F. to cause further separation of wax. The wax separating at thisstage is of relatively lower melting point than the Wax removed in theinitial stage. The chilled mixture is passed via line 99, controlled byvalve |00, and pumped by pump through line |0|a into filter |02, fromwhich the separated low melting point wax containing some solvent isremoved via line |03 controlled by valve |04 and pumped by means of pump|05 through heat exchanger |05a and into evaporator |06. Evaporator |06is similar to previously described evaporator 42 and is heated by meansofclosed steam coil |01 and contains mist extractor |08. Low meltingpoint wax is removed from evaporator |06 through line |09 controlled byvalve ||0 and pumped by means of pump into low melting -point waxstorage tank l2. The solvent vaporized in evaporator |06 is passed vialine ||3 controlled by valve ||4 into line ||5 and through condenser ||6and line ||1 controlled by valve ||8 into line 5| and pumped by pump 52to mixed solvent storage tank 53. The ltrate from lter |02 consisting ofsubstantially completely dewaxed oil and mixed solvent is passed throughline ||9 and heat exchanger |20 into evaporator l2 which is similar topreviously described evaporators 42 land |06, wherein the solvent isvaporized from the dewaxed oil. Dewaxed oil is removed from evaporator|2| through line |22 controlled by valve |23 and pumped by means of pump|24 into dewaxed oil storage tank |25. The mixed solvent vaporized fromthe dewaxed cil is removed from evaporator |2| through line |26controlled by valve |21 and passed into line ||5 and thence to mixedsolvent storage tank 53 as described for the solvent vaporized fromevaporatorl |06.

It is generally desirable to wash the Wax cake on the lter with mixedsolvent, the solvent being at substantially the filtering temperature ofthe wax-oil-solvent mixture. Mixed solvent can be obtained from line||1, or by means of connections not shown from storage tank 53, andpassed through line |28 controlled by valve |29 through cooler |30 andthence through line 3| controlled by valve |32 and line |0|a into lter|02. The washings are passed from lter |02 into line ||9 and handled inthe manner described for the filtrate removed from this filter.

A modiiication of the solvent recovery process is necessitated ifsolvent A cannot be separated from solvent B by simple distillation dueto azeo.- trope formation. Thus, if benzene or a mixture of benzene andtoulene is employed as solvent A with methyl ethyl ketone as solvent Bseparation cannot be readily effected by simple distillation due toazeotrope formation between the benzene and methyl ethyl ketone. In thiscase the mixed solvents obtained from the rst stage through line 49controlled by valve 50 or obtained from the second stage through line||1 controlled by valve IIS are passed through line |33 controlled byvalve |34 and pumped by means of pump |35 into extractive distillationcolumn |36. Column |36 may be a plate type column or may be a packedcolumn as indicated for distillation column 19, packing beingrepresented by |31. Heat is supplied to this column by closed steam.coil |38. The solvent mixture enters at a point near the bottom of thecolumn and passes upward through the column countercurrent to the now ofan extractive solvent such as ethylene glycol, diethylene glycol and thelike, which solvent boils at least 20 F. and preferably 50 F. above theboiling point of any component of solvent A and has a greater ainity forsolvent B than for solvent A. The extractive solvent is passed fromstorage tank |39 through line |40 controlled by valve |4| and pumped bymeans of pump |42 into extractive distillation column |36 at a pointnear the top of the column. The temperature within the column ismaintained at such a point that solvent A is vaporized and removed asvapor from the top of the column and solvent B, dissolved in theextractive solvent, is removed from the bottom of the column. Vaporizedsolvent A is removed from the column through line |43 controlled byvalve |44, passed through condenser |45 and pumped by means of pump |46through line |41 controlled by valve |48 into line 95 and thence intosolvent A storage tank 2|.

The extractive solvent solution of solvent B is removed from the bottomof column |30 via line |49 controlled by valve |50 and pumped by pump|5| into distillation column |52. Distillation column |52 is similar todistillation column 19. In this column solvent B is vaporized and theextractive solvent is removed as bottoms through line |53, controlled byvalve |54, and pumped by means of pump |55 via line |56 into extractivesolvent storage tank |39. Vaporized solvent B is removed from the top ofdistillation column |52 via line |51 controlled by valve |58 and passedthrough condenser |59 from which it is pumped by means of pump |60through line |0| controlled by valve |62 and passed via line 81controlled by valve 88 into solvent B storage tank 29.

The rate of chilling of the wax-oil-solvent A mixture in chiller I 4maybe varied within wide limits Without affecting the lterability of theresultant wax. Chilling rates between 0.5 F. and 20 F., or even higher,may be employed. Even shock chilling of the mixture of wax, oil andsolvent A will result in the separation of a gelatinous wax which isconverted into a readily rllterable wax upon addition of solvent B.

When separating wax-oil mixtures containing high proportions of wax andrelatively low proportions of oil such as, for example, crude waxes orslack waxes, it is often desirable to dilute the chilled mixture of Wax,oil, solvent A and solvent B before ltering with a portion of the ltrateobtained in the ltering operation. Inl order to 11.. effect thisdilution, ltrate is returned from line 5S to line 35a through line |53controlled by valves 104 and |65, by means of pump |66. The amount offiltrate returned in this manner may be as high as about 2 or 3 volumesper volume of original wax-oil mixture, although generally about 1volume of the ltrate is so returned.

The amounts of solvent, as well as the proportions of solvent A andsolvent B in the solvent mixture, will depend upon the character of theWax-oil mixture to be separated and particularly upon the viscosity and/or viscosity index of the oil present in the wax-oil mixture. Ingeneral, the total amount of solvent including both solvent A andsolvent B Will not be greater than about 10 volumes, and probably notless than about 0.5 volume per volume of Wax-oil mixture. Usually theamount of solvent will be between about 1.5 and 6 volumes per volume ofwax-oil mixture. However, it is essential that the solvent solution ofoil in the chilled mixture be sufliciently non-viscous that iiltrationmay be readily effected. The larger proportions of solvent will beemployed in dewaxing those waxoil mixtures containing relatively lowpercentages of wax, and in which the oil is f high viscosity indexand/or viscosity. ri'hus, as much as 8 or 1U volumes of total solventper volume of Wax-oil mixture may be employed in dewaxing viscouslubricating oil rainates. In dewaxmg distillates and ralnates generallybetween about 2 volumes and about 6 or 7 volumes of total sol vent pervolume of the distillate or raffinate will be employed. The lowersolvent ratios are generally employed in the separation of wax-oilmixtures generally referred to as crude or slack wax and the like. Suchseparations may be considered as deoiling processes because the primaryobject is to obtain an oil-free wax. In such deoiling operations,between about 0.5 and or 6 volumes of solvent per volume of crude waxmay be employed although 11/2 to 4 volumes of solvent are usuallyemployed.

The volume ratio of solvent B to solvent A must be less than to 1 andgreater than about 0.67 to 1. Smaller proportions of solvent B areinsufficient to effectively convert the gelatinous mass into a readilyfilterable form which will produce an easily washable filter cake.Preferably the ratio will be in the range of about 7.5 to 1 and 0.9to 1. Equal proportions by volume of solvent A and B, i. e. a ratio of 1to 1, have been found to be particularly effective in separating a widevariety of wax-oil mixtures. The ratio which is most effective for anygiven separation will depend upon the viscosity and the viscosity indexof the oil associated with the Wax in the wax-oil mixture to beseparated. The lower ratios of solvent B indicated above Will beemployed to separate those mixtures containing high V. I. and/or highviscosity oil. Moreover, the temperature of dewaxing or deoiling willalso influence the ratio to be employed. In general, the lower thedewaxing or deoiling temperature the lower will be the ratio of solventB to solvent A in the mixture of solvents employed. The higher ratios ofsolvent B to solvent A indicated will be employed in the treatment ofwax-oil mixtures containing oil of relatively low viscosity and/or lowviscosity index. Thus, low viscosity distillates will require a higherratio of solvent B to solvent A than the high viscosity distillates orthan the rainates from the low or high viscosity distillates. The higherratios are also employed generally in deoiling crude waxes and the like.In selecting the particular ratio of solvent B to solvent A for anygiven separation, it is desirable that suiiicient solvent A be added sothat the Wax separating on chilling will be of the gelatinous type andthat on the addition of solvent B, at dewaxing or deoiling temperatures,the resulting product consists of a rejected, easily lterablecrystalline wax suspended in an oil-solvent mixture consisting of asingle liquid phase. If the proportion of solvent A is too low there maybe two liquid phases present in the chilled mixture; one consisting ofoil containing a small amount of solvent, and the other consisting ofsolvent containing relatively small amounts of oil. This condition is tobe avoided.

In the description of the invention it has been stated that solvent A isadded to the mixture of wax and oil at a temperature such that the waxis in solution, or miscible, with the oil and the resulting mixturecooled to the dewaxing or deoiling temperature. It is to be understood,however, that if a portion of the solvent A to be employed is addedwhile the wax is completely in solution in the oil the remainder may beadded in increments during the chilling of the wax-oil mixture. The rateof addition of solvent A must be sumcient to cause the wax whichseparates to be of the gelatinous type. If insuicient solvent A ispresent during the chilling, wax separates out in poorly defined crystalmasses which seriously reduce lter rates of the resulting products. Itis essential in carrying out the process of this invention thatsubstantially no crystal formation occurs during the chilling. Thus, incarrying out the process of the invention a mixture of wax and oil maybe mixed with, for example, 10% or more of the total amount of solvent Ato be employed, and as the mixture is chilled, further increments ofsolvent A may be added. All of the solvent A should be added by the timethe temperature of the wax-oil-solvent mixture reaches the desireddewaxing or deoiling temperature. At this temperature, precooled solventB is added to produce the lterable wax. In some instances improvedfiltration rates have been observed when the chilling of the wax-oilmixture has been carried out with incremental addition of solvent A. l

Furthermore, it is within the scope of the invention to treat wax,particularly petroleum wax, which is present at any given temperature asa gelatinous type wax containing or being associated with solvent withor without oil. to convert this gelatinous type wax into a readilylterable physical form, regardless of how such gelatinous Wax isproduced.

In the description of the process of this invention it has been assumedthat solvent A and solvent B are completely separated after use forreuse in the process. While it is desirable and, in fact, preferred thatpure solvent A be returned in the process as indicated and pure solventB be added at the dewaxing temperature, the solvent A which is added tothe wax-oil mixture before chilling may contain small amounts of solventB providing the amounts of solvent B are insufficient to prevent theformation of the gelatinous, unllterable waxy reject on cooling.Moreover, solvent B may contain small proportions of solvent A providingthat it contains a sufcient amount of solvent B or at least hassufficient wax anti-solvent characteristics to cause the change instructure from the uni'llterable to the readily lterable form. For thesereasons it ls not essential that complete separation of sol- 'acentos'vent A from solvent B be eected in the recovery stage. It has beenfound, for example, that solvent A containing a few per cent to as muchas about by volume of solvent B in some instances produces the describedunlterable wax during the initial chilling. Moreover, it has been foundthat solvent B containing a few per cent to as much as 10% by volume ofsolvent A may be added to the chilled mixture to effect the desiredconversion of the unlterable wax into readily filterable, ycrystallineform.

The amount of solvent employed for washing the wax cake on the filter isgenerally about 1 volume of the mixed solvent, using the substantiallysame ratio of solvent A to solvent B as is present in the filtrate, pervolume of the original wax-oil mixture, although as much as 3 to 4volumes of the mixed solvent may be employed and in some cases as littleas 0.25 to 0.5 volume of the solvent may suffice. The object of washingis to remove oil retained in the wax cake after filtering so that theamount of solvent employed for washing will depend to a certain extenton the ease of washing and upon the quality of wax desired. Wax cakesformed by the process of this invention are found to be readily washedwith between about 0.5 volume and 1 volume of solvent to producesubstantially oil-free wax cake.

Dewaxing aids of various sorts are employed in many dewaxing operationsand they may be used in the process of this invention with benecialresults. It is to be pointed out that such aids are apparently notnecessary in that readily fllterable waxes have been produced fromsubstantially all types of wax-oil mixtures without their use. Incertain cases dewaxing aids such as oxidized waxes, particularlyoxidized petroleum waxes, asphaltic materials, polyvalent metal soaps offatty acids such as aluminum stearate and the like may improve filteringand washing rates.

These materials may be added to the wax-oil mixtures before chilling.

The following examples will further illustrate the invention.

Example I A sample of an SAE l0 waxy furfural refnate from aMid-Continent crude oil was treated following the process of thisinvention and, for comparison, following conventional dewaxing methodsfor the separation of high melting point wax.

In the first case to 50 grams of the waxy rafnate, heated to 150 F. toeffect solution of all of the wax in the oil, was added 75 ml. of amixture of 90% benzene and 10% toluene, and the resulting mixturechilled, at the rate of about 1.5" F. per minute, with stirring to 35 F.To the chilled mixture was added 75 m1. of MEK precooled to 35 F. andthe resulting mixture ltered through an 11 cm. Buchner funnel. The waxcake was washed with 75 ml. of a mixture of 50% MEK, 45% benzene and 5%toluene'precooled to 35 F.

A second 50-gram portion of the waxy raflinate was heated to 150 F. inthe presence of 75 ml. of a mixture of 50% MEK, 45% benzene and 5%toluene, the mixture chilled at the samerate with stirring to 35 F. andmixed with an additional 75 ml. portion of solvent of the compositioninitially employed precooled to 35 F. The resulting slurry was filteredin the same manner as above and the wax cake washed on the filter with athird 75 ml. portion of the mixed solvent 'also precooled to thefiltering temperature.

The results of the above experiments are pr-1 sented in the followingtable:

Chilling in presence of Convensolvent A; tional then adding dewaxingsolvent B Yield of wax, percent by weight 8i 6 7. 6 Melting point ofwax, F.- 159. 5 161 Filter time, minutes 0. 50 1. 00 Washing time,minutes 1. 30 2. 60

Example II Example I was repeated, using an SAE 70 waxy furfural rafatefrom Mid-Continent crude oil. The data are presented in the followingtable:

Example III A sample of an SAE 20 rail-mate from Mid-Continent crude wasdewaxed under conditions designed' to produce a substantially oil-freewax directly from the raffinate. The dewaxing was carried out accordingto the process of the invention and by conventional means forcomparison. In the first case 50 g. of the waxy raffinate was dilutedwith 50 ml. of toluene, the mixture heated to 150 F. and chilled to 35F. at a. rate of about 1.5 F. per minute. To the chilled mixture wasadded 50 inl. of MEK precooled to 35 F. The resulting slurry wasfiltered and washed on the filter with 75 inl. of equal parts of tolueneand MEK.

A 50 g. portion of the same waxy raffinate was heated to 150 F. andchilled to 35 F. with incremental addition of solvent consisting ofequal parts of toluene and MEK. A total of ml. of the mixed solvent wasadded by the time the temperature of the mass was 50 F. The resultingslurry was filtered and washed on the filter with 75 ml. of the samemixed solvent.

Data regarding the yields and lter times for the two methods of dewaxingare shown in the following table:

Chilling in presence oi Convensolvent A; tional then adding dewaxlngsolvent B Yield of wax percent by weight. 8. 8 9.0 Melting point, F 14714s Filter time, minutes 0. 75 1. 42 Washing time, minutes l. l2 l. 67

Example IV filter with 75 ml. of precooled solvent consisting of equalparts of toluene and MEK.

A second 50 g. portion of the waxy raffinate was mixed with 75 ml. oftoluene and '75 ml. of MEK. The mixture was chilled to 0 F. andfiltered. The wax cake was washed on the .lter with 75 ml. of equalparts of toluene and MEK precooled to the ltering temperature.

A third 50 g. portion of the waxy raffinate was heated to 150 F. andchilled to 0 F. During the chilling 150 ml. of equal parts of tolueneand MEK was added; 50 m1. at 70 F., 50 ml. at 50 and 50 ml. at 20 F. Theresulting slurry was filtered and the wax cake washed on the nlter with75 ml. of the same mixed solvent precooled to 0 F.

The results of the three above experiments are shown in the followingtable:

Example III, repeated using in each .method 50 g. of the waxy raiinate,25 ml. of toluene and 75 ml. of MEK, gives results comparable to thoseshown in the table of Example III. Filtering times in the case of theconventional method are approximately double those obtained by followingthe method of this invention.

Example VI Example IV, repeated using acetone in place of MEK in eachinstance, gives filter rates similar to those shown in the table ofExample IV. Using the conventional deoiling process the filter rates arelower than when the crude wax is chilled in the presence of toluenealone and acetone added at the temperature of filtration.

Eixample VII Example IV, repeated using isopropyl alcohol in place ofMEK, gives filter times slightly greater than those obtained `using MEK.However, chilling in the presence of toluene and adding precooledisopropyl alcohol at the temperature of filtration gives appreciablyhigher filtration rates than when following conventional dewaxingmethods.

Example VIII To determine the eiect of cooling rates on nltration ratesof the resulting wax-oil-solvent ,slurries three 50 g. portions of awaxy raffinate from a California waxy crude oil long residuurn, whichraninate was prepared by selective solvent extraction using a mixture ofpropane and phenol, were each mixed with 100 ml. of toluene, heated to150 F. and the resulting mixtures chilled to 0 F. using chilling ratesof 10 F., 3 F. and 1 F. per minute respectively. At 0 F. 100 ml. of MEKprecooled to 0 F. was added to each chilled mixture and the resultingslurries were filtered. The wax cakes were each washed on the lter with100 ml. of a preoooled mixture of equal parts of toluene and MEK.

For purposes of comparison a sample of the `same waxy rafhnate wasdewaxed by conventional methods. A `50 g. .portion was Vn iixel .with100 ml. `of `a mixture of equal parts yof toluene and heatedto 150 F.and chilled to 0 F. using .chilling rates of about 1.5 F. per minute.The chilled mixture was diluted with a second ml. portion of the mixedsolvent precooled to 0 and iiltered. The wax cake was washed on the lterwith 100 ml. of the mixed solvent precooled to the filteringtemperature.

Chilling in presence of solvent 632231' A; then adding solvent B dewaxngCooling rate, P F. per

minute l0 3 1 1. 5

Yield of wax, percent by weight 23, s 2i. i 26. 4 32. t Melting point, F153 152 152 143 Filtervtime, minutes. l. 10 l. 20 l1.45 3. 0 Washingtime, minutes 2. 85 2. 40 2. 85 3.0

Example IX A sample of crude wax (petrolatum) obtained by dewaxing aMid-Continent bright stock was deoiled in the following manner. Amixture of 5 0 g. of the petroiatum and 75 ml. of toluene was heated toF. and then chilled to 40 F., at which temperature 75 ml. of precooledMEK was added and the resulting mixture ltered, the wax cake beingwashed on the lter with 75 ml. of a mixture of equal parts of MEK andtoluene precooled to the ltering temperature.

For comparison a second 50 g. portion of the petrolatum was mixed with75 ml. of equal parts of toluene and MEK, heated to 150 F., chilled to40 F., at which temperature 75 ml. of the same mixed solvent precooledto 40 F. was added, and the mixture filtered and washed on the filterwith 75 ml. of the mixed solvent which had also been precooled.

A third 50 g. portion of the petrolatum was heated to 150 F. and chilledto 40 F. with incremental addition of a solvent consisting of equalparts of toluene and MEK. A total of 200 m1. of solvent was added duringthe chilling. The chilled mixture was filtered and washed on the lterwith 75 ml. of the same mixed solvent precooled to 40 F.

The results of the three operations are shown in the following table:

A crude wax obtained by conventional dewaxing operations from an SAE 40propane-phenol raffinate from waxy California crude was deoiled by themethods of this invention and, for comparison, by conventional methods.A 50 g. portion of the crude wax was diluted with 50 Inl. of toluene,heated to 150 F. and chilled to 35 F. To the chilled mixture was added50 ml. of precooled MEK and the mixture filtered and washed with 75 ml.of solvent at the same temperature. The wash solvent consisted of equalparts of toluene and A second 50 g. portion of the .crude wax wasChilling in presence of Convensolvent A; tional then adding deoilingsolvent B Yield of wax, percent by weight. 54. 6 52. 4 Melting point, F160 160 Filter time, minutes. 0. 80 1. 75 Washing time, minutes 2. .404. 25

Example XI Example X, repeated using 60 ml. of toluene and 40 m1. of MEKin place of equal parts of toluene and MEK, givesresults substantiallythe same as those shown in the table of Example X.

Example XII Example X, repeatedusing '70 m1. of toluene and 30 ml. ofMEK in place of 50 m1. each'of these solvents, gives ltration times ofover 3 minutes for the sample chilled in the presence of toluene aloneand 2 minutes for the sample chilled in the presence of mixedtoluene-MEK, thus entirely losing the advantage of chilling in thepresence of toluene alone.

Example XIII An SAE 40 distillate from California waxy crude oil wasdewaxed using proportions of solvent A to solvent B found to bedesirable and, for

comparison, using proportions of solvent B (waxy anti-solvent) below thelimits found to be satisfactory. Using the low proportions of solvent B,this solvent was added before and after chilling to determine the effectof its presence during the chilling. In the following experiments therst two were carried out in accordance with the teaching of thisinvention using ratios of solvent B to solvent A of 1 to 1 but varyingthe ratio of total solvent to sample of distillate. In experiment (A)the latter ratio is 7 to 1 and in experiment (B) the ratio is 4 to 1.The second two experiments show the ineffectiveness of small amounts ofsolvent B. In experiment (C) using a ratio of total solvent to sample ofabout 3.82 to 1 and a ratio of solvent B to solvent A of about 0.097 to1 the chilling was effected in the presence of solvent A and solvent Bwas added to the chilled mixture. The same solvent ratios were employedin experiment (D), however in this case chilling was eiected in thepresence of both solvent A and solvent B.

(A) A 50 g. sample of the above waxy distillate was diluted with 175 ml.of toluene, chilled to 0 F. and to the chilled mixture was added 175 m1.of MEK precooled to 0 F. The resulting slurry was iltered and the waxcake washed on the filter with 50 ml. of equal parts of toluene and MEKwhich had been precooled to the ltering temperature.

(B) A second 50 g. portion of the waxy distillate was dewaxed followingthe method outlined in (A) except that 100 mlfof toluene and 100 ml. ofMEK was `employed in` place of the 175 ml. in each case.

(C) A third 50 mL-portion of the waxy distillate was diluted Awith 175ml. of toluene, the

mixture chilled to 0 F. `and to the shined migf ture was added 17 ml. ofMEK precooled to 0 F. and the resulting slurry ltered and washed on thiilter v'v'itl'i 50 ml. of solvent consisting of 89% toluene and 11% rmxpreooied to of F. j

(D) A fourth 50 g. portiri of the waxy distillate was diluted with 175inl. of toluene and 17 m1. Of MEK. The eS'llltng mixture heated t F. andchilled to 0 F. The chilled mixture was filtered and the wax cake Washedon' the filter with 50 ml. of a mixture of 89% toluene and 11 MEKprecooled to 0 F.

Data regarding the four above experiments are shown in the followingtable:

Chilling in pres- D ewaxing using thglfl s small proportions solvent Bof solvent B (A) (B) (C) (D) Yield of wax, percent by weight 12.2 12.19. 4 10. 4 Melting point of wax, F. 147 147 150. 5 149 Filter time,minutes.- 1. 5 0.9 3. 88 2. 23 Washing time, minutes. 1.03 l. 0 4. 623.0

Example XIV A sample of the waxy raffinate described in Example VIII wasdewaxed using relatively low ratios of solvent B to vsolvent A in orderto determine the effectiveness of these low ratios in producing lterableslurries in dewaxing operations applied to rafnates.

One 50 g. portion of the waxy ramnate was dewaxed following the methodof experiment (C) of Example XIII and a second 50 g. portion was dewaxedas 4described in experiment (D) of the same example.

Data regarding these two operations are shown in the following table.Refer to the table in Exarnple'VIII for filtration rates on slurriesproduced from the same waxy raffinate by methods of this invention.

iDe'waxin'g using low MEK to toluene ratios l Adding MEK Chilling in tochilled presence of mixture mixed solvent Yield of wax, percent byWeight 33. 4 9 20. 6 Melting point, F 149 Filter time, minutes 19 19 1819 Washing time, minutes Example XV Example XVI Filtration studies todetermine relative filtration rates of wax-oil-solventslurries preparedaccording to the methods of this invention and those prepared byconventional processes have lbeen carried out in pilot plantequipmentsuch as is-generally usedvto estimate filtration times in commercialrotary lter operations. In these tests, filter leaves having an area of0.239 sq. ft.

and .coveredwith a commercial lter cloth were employed. The filterleaves were completely immersed in the Vwax-,oil-solvent slurry and avacuum ofr 20 inches4 o f mercury applied tothe leaves until a cake of.desirable thickness (about ,1A inch thick)r was formed. The filter leafwas then removed from the slurry. allowed to dryfor a few seconds,immersed in fresh solvent with the vacuum still being applied to thesystem and nally given a second drying period.v

Total ltration rates including filtering, washing and drying were4calculated.in terms "of pounds of wax per square foothoi filteringsurface per hour, and gallons 'of 'solvent-free filtrate per square footof ltering surface per hour.

, .Wax slurries were prepared by the methods of thisji'nvention and byconventional methods for use in the above described filtration tests.One

slurry was prepa-red by 'chilling 1500 g. (1715 ml.) of ethe waxyrainate described in Example VIII in the presence of 3000 ml. of tolueneto 0 'F. and adding 3000 ml. of MEK precooled to 0 F. The second slurrywas prepared by chilling 1 000 g. '(1143 ml.) of the same waxy rafdnateiand2000 ml. of an vequal volume mixture of MEK and toluene and adding asecond 2000 ml. portion of the same mixed solvent precooled to 0 F. whenthe chilled mixture reached 0 F. The resulting slurrie's were found tohave the following filtrate rates, and .the waxjand'oil recovered `ineach case had the .following characteristics:

.The foregoing description of my invention is not to be taken aslimiting my invention but only as illustrative thereof since manyvariations may be made by those skilled in the art without departing'from the scope of the following claims.

1. A method of converting a normallycrystalyline petroleum wax which hasbeen precipitated Ifrom an oil-aromatic solvent solution in an un-'lterable gelatinous form into a readily'lterable form, without changingthe temperature, which comprises contacting the gelatinous wax with anvamount by volume of a wax anti-solvent atleast ,as great as aboutiii-parta per 1.5 parts of aromatic solvent. said aromatic 'solventconsisting essen- 'tiallyofan aromatio'hydrccarbon.

2. A method o f converting an unfilterable: ge-

latinous mixture Vof wax, oil and aromatic Vsolventconsistingesseritiallyl o f'an aromatic hydrocarbon into areadilyiilterable slurry of `wax in oil and solvent which comprisescontacting said gelatinous mixture with vanamount by volume of awax-anti-solventiat least as great as 1 part to 1.5 parts of aromaticsolvent.

3. Aprocess for'V the separation Aof wax-oil mixtures which comprises`chilling said wax-oil mixjture-inthe presence'of 'an aromatic solventconsisting essentially 'o f "an varomatic hydrocarbon to ja temperatureVsufcien'tfto cause the separation of wax `in an uniiiterable'gelatinousform, adding to the vchilled mixtureja waxanti-solvent p re-A l cooledto labout the temperature ofthe'chilled 2O mixture and in the amount byvolume of at least 1 pa`rt per 1.5 Aparts of aromatic solvent, andseparating the resulting solvent solution of oil from wax.

4. A process as in claim 3 in which said aromatic solvent is toluene.

5. A process as in claim 3 in which said aromatic solvent comprisesbenzene.

6. A process las in claim 3 in which said Wax anti-solvent is a ketone.

7. A proc'esfsjas in claim 3 in which said wax anti-solvent is 8.Aprocess as in claim 3 in which said wax anti-solvent comprises acetone.9. A process for the separation of wax from wax-oil mixtures whichcomprises chilling said wax-oil mixture in the presence of an aromaticsolvent consisting essentially Aof an aromatic hydrocarbon to produce annnlterable gelatinous mass, 'adding to rthe chilled mixture 'a waxVantisclvent jprecooled to about `the temperature -of said 'chilledmixture, the volume ratio of wax anti-solvent 'to aromatic solvent beingat least 0.67 to 1, to convert said gelatinous mass into a readilyllterable slu'r'ry of wax in a solvent solution of o il and "separatingsaid wax from said slvent'solution 'of oil.

l0. A process for the 'separation of wax-oil mixtures which comprisesadding to said mixture an aromatic solvent consisting essentially 'of anaromatic hydrocarbon Vfrom which Waxse'parates on cooling in agelatinous non-iilterable form, cooling the wax-oil-'solvent solution toa temperature su-cient to cause the separation of at least a portionofthe wax, 'adding a precooled wax anti-solvent at approximately Ythe sametemperature 'as the cooled wax-oil-solvent rto convert the 'gelatinous"vi/'ax pr'esentin the mixture into'a'readily lterable form andseparating the resulting solvent =`solution of oil rfrom said readilylterable wax, the vamount by volume of wax anti-solvent'added being atleast as great vas about f1 part per 1.5 p'a'rts of aromatic solvent.

ILA process for the "separation of 'waxio'il mixtures Whiohcomprisesbringing saidmixture lto -a state wherein 'the 'Wax is substantiallyYcompletelydissolvdfintiie oil present in `said mixture, adding theretoan aromatic solvent fconsisting essentially of *an aromatic hydrocarbonfrom 'which wax spar'ats'upon'cooling infanuniilterable gelatinous form,'chilling the wax-oilsolvent "mixture to cause the 'separation of-atvleast 'a portion of the wax'preseht'in'saidiwaxoil mixture inagel-atinous form, adding to the chilled w'ax-oillsolv'e'nt mixture 'aprecoole'd wax "anti-solvent Aat 'substantially the "same temperature'asth'e"'WaX-oil-solventinixture to convert thegelatinou's vv'aI-x intoa readily iilte'r'ablef'form land separating 'the readily 4iilterablewax 'from the oil-solvent mixture, the 'volumeratio of 'wax anti-solventto aromatic solvent being 'between 0.67 and 1'0to`1.

12. A-processas inclaim 11 in'wliich said waxoilsolvent mixture ischilled 'to 'a temperature between ""F.- and '-25 F.

13. 'fl-process 'asinfclaim 11 in which thevolume of waxanti-s'olvent'to'aromatic solvent is between 0.9 and 7.5 to 1 and the byvolume? ratio of total-*solvent to wax-oil mixture is between 0.5and-101ml. y l l 14.1 A L'J'rocess as in -`claim 11- in whichtheaiiomatic solvent is tolueneand the wax anti-solvent is MEK.

15'A- -proc ess for the s epa'rationfof high melt- 'ring pointfwax' froma Wax-oil mixture containing both high melting point and low meltingpoint Wax which comprises bringing said Wax-oil mixture to a statewherein the wax present is substantially completely dissolved in theoil, adding to the wax-oil solution an aromatic solvent consistingessentially of an aromatic hydrocarbon from which wax separates oncooling in an unlterable gelatinous form, cooling said solventwax-oilmixture to a temperature in the range of about 75 F. to about 25 addingto the chilled mixture a wax anti-solvent which has been precooled tosubstantially the same temper- -ature as the chilled sclvent-wax-oilmixture to convert gelatinous wax into wax of a readily lterablephysical form and separating said readily lterable wax from the solventsolution of oil containing low melting point Wax, the volume ratio ofwax anti-solvent to aromatic solvent being between 0.67 and 10 to 1.

16. A process for the separation of high melting point Wax and lowmelting point wax from wax-oil mixtures containing both high and 10Wmelting point waxes which comprises bringing said wax-oil mixture to astate wherein the wax present is substantially completely dissolved inthe oil, adding thereto an aromatic solvent consisting essentially of anaromatic hydrocarbon, chilling the resulting mixture to a temperaturebetween about 75 F. and 25 F. to cause the separation of high meltingpoint wax in an unfilterable gelatinous non-crystalline form, adding tothe chilled mixture a wax anti-solvent precooled t substantially thesame temperature as said chilled solvent-wax-oil mixture to convert theseparated wax into a readily iilterable crystalline form, separating thereadily lterable high melting point wax from a solution of low meltingpoint wax, oil and solvent, further cooling the solvent-oil-low meltingpoint wax mixture to a temperature between about F. :and about 25 F. tocause the precipitation of low melting point wax and separating lowmelting point wax from the solvent solution of substantially completelydewaxed oil, the volume ratio of Wax antisolvent to aromatic solventbeing between 0.67 and 10 to 1.

17. A process according to claim 3 in which said wax anti-solventcomprises a ketone.

18. A process for the separation of Wax from Wax-oil mixtures whichcomprises adding to said wax-oil mixture an aromatic solvent consistingessentially of an aromatic hydrocarbon containing not more than 10% byvolume oi a wax antisolvent, chilling the wax-oil solvent mixture toproduce an unlterable gelatinous mass, adding to the chilled gelatinousmass a wax antisolvent containing not more than 10% by volume ofaromatic solvent at substantially the same ternperature as the chilledgelatinous mass t0 convert the gelatinous mass into a readily lterableslurry of wax crystals in a solvent solution of oil and separating saidwax from said solvent solution of oil, the ratio of Wax anti-solvent toaromatic solvent being at least as great as about 0.67 to 1.

P. STANLEY BACKLUND. VANCE N. JENKINS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,049,059 Goss et al. July 28,1936 2,067,050 Govers Jan. 5, 1937 2,223,939 Jones Dec. 3, 19402,229,658 Jenkins Jan. 28, 1941 2,463,845 Backlund et al Mar. 8, 19492,486,014 Evans Oct. 25, 1949

1. A METHOD OF CONVERTING A NORMALLY CRYSTALLINE PETROLEUM WAX WHICH HASBEEN PRECIPITATED FROM AN OIL-AROMATIC SOLVENT SOLUTION IN ANUNFILTERABLE GELATINOUS FORM INTO A READILY FILTERABLE FORM, WITHOUTCHANGING THE TEMPERATURE, WHICH COMPRISES CONTACTING THE GELATINOUS WAXWITH AN AMOUNT BY VOLUME OF A WAX ANTI-SOLVENT AT LEAST AS GREAT ASABOUT 1 PART PER 1.5 PARTS OF AROMATIC SOLVENT, SAID AROMATIC SOLVENTCONSISTING ESSENTIALLY OF AN AROMATIC HYDROCARBON.
 15. A PROCESS FOR THESEPARATION OF HIGH MELTING POINT WAX FROM A WAX-OIL MIXTURE CONTAININGBOTH HIGH MELTING POINT AND LOW MELTING POINT WAX WHICH COMPRISESBRINGING SAID WAX-OIL MIXTURE TO A STATE WHEREIN THE WAX PRESENT ISSUBSTANTIALLY COMPLETELY DISSOLVED IN THE OIL, ADDING TO THE WAX-OILSOLUTION AN AROMATIC SOLVENT CONSISTING ESSENTIALLY OF AN AROMATICHYDROCARBON FROM WHICH WAX SEPARATES ON COOLING IN AN UNFILTERABLEGELATINOUS FORM, COOLING SAID SOLVENT-